This invention relates to sealants and more specifically to sealant compositions which are asbestos-free.
Asbestos incorporated into sealant systems is well-known in the industry. One such system, incorporating asbestos, is preformed sealant tape which can be used in applications such as a bedding and face glazing compounds which make seals to such substrates as metals, glass, ceramics and plastics. Typically, such asbestos-based sealant tape uses a base stock containing an inorganic filler such as calcium carbonate and a suitable binder such as a polybutene or a mixture of polybutene and polyisobutylene. Formulations of filler, binder and asbestos vary according to a specific application. For example, a bedding compound useful in forming metal to metal bonds such as those produced in the manufacture of mobile homes, typically uses only polybutene as a binder. However, a high quality tape sealant, useful in the automotive industry, which needs greater bond strength, good aging properties and the ability to adhere to porous and nonporous substrates typically contains, as a binder, substantial quantities of polyisobutylene together with polybutene.
Because of environmental and health problems associated with asbestos, there is an immediate need in the sealant industry for asbestos-free sealant systems which have good sealant properties and which can be manufactured at reasonable cost. Systems incorporating substantial amounts of butyl rubber will perform adequately, but generally are commercially unacceptable because of high cost. It is an object of our invention to produce an asbestos-free sealant system which demonstrates adequate sealant properties at reasonable cost.